The present invention relates to electrical power supplies. More specifically, the invention relates to a converter having a dc line.
A down chopper of a dc-dc converter receives dc current from a dc power supply, modulates or xe2x80x9cchopsxe2x80x9d the current to reduce current amplitude, and provides the chopped current on a dc line. The reduction in current is proportional to duty cycle of the chopping.
On-off action of the down chopper creates a pulse train-type pattern in the chopped current. Consequently, the chopped current on the dc line contains harmonic frequency content.
The dc-dc converter may also include an EMI filter for reducing the harmonic content to acceptable limits. A conventional EMI filter includes passive inductance, capacitance and resistance elements, the values of which are determined by power rating, chopping frequency and filter attenuation requirements. The EMI filter typically constitutes a significant amount of the overall weight of the dc-dc converter.
Reducing the weight of EMI filters for dc-dc converters used in aircraft would be very desirable. Reducing the weight would lower aircraft fuel consumption. Lowering the fuel consumption, in turn, would lower the cost of flying the aircraft.
According to one aspect of the present invention, an apparatus includes a converter having a dc line, and an active filter coupled to the dc line. The converter is operable to provide a pulsed current on the dc line at a chopping frequency; and the active filter is operable to trap a fundamental of the pulsed current. The active filter allows a substantially smaller passive filter to remove remaining harmonic frequency components.